Graphite is the stable modification of carbon under normal conditions and has been used for many years in various sectors such as the steel- and automotive industries. In the next few years, the area of renewable energy, which is experiencing extremely rapid growth in the context of electromobility, will offer the highest growth potential for graphite, as it is used as a raw material for anodes in lithium-ion batteries. Approximately 10 to 15 times more graphite than lithium is required for one lithium-ion-battery.
Globally, graphite occurs most commonly as so-called flake graphite, which are graphite flakes containing only a small proportion (maximum 20%) of actual graphite finely distributed in rock. This natural graphite must be processed using various methods in order to obtain the final product which is used for battery applications and has a purity of over 99.95%. As well as the chemical purity, the morphology of the graphite also plays a decisive role. Spherical graphite (SPG) is ideal for the application as a raw material for anodes. Its smooth, small surface prevents flaking and means low irreversible capacity loss and long service life. Thanks to the high tap density, high charging is achieved and consequently a higher energy density.
During the previously most frequently used cascade process for the spheroidization of graphite, the graphite concentrate passes through a machine train· of more than 20 classifier mills installed in rows with external classifiers. As well as the enormous amount of space required, there are further disadvantages, i.e. each mill must be adjusted separately, and a scale-up of the production capacity is only possible by adding further, more complex machine trains. This assembly offers a complete lack of flexibility and a rapid change between individual product particle sizes is practically unrealizable in such a setup, as the complete machine train is optimized to suit one specific particle size.
The system developed has overcome all the disadvantages of the standard technology and delivers an elegant solution for efficient, process-technology optimized graphite rounding. In a first step the flake graphite is pre-ground to the optimum initial particle size for spheroidization in a classifier mill or fluidized bed jet mill. The actual particle rounding takes place directly downstream in the newly designed Netzsch GyRho Rounding Unit which is available in various construction sizes and can be specially designed to suit the necessary output quantity. For larger throughput volumes two (or more) machines can be operated simultaneously and replace the train of 20 machines or more as mentioned above.
Read more at Netzsch here